The nature of “dark” gamma-ray bursts

Greiner, J.; Krühler, T.; Klose, S.; Afonso, P.; Clemens, C.; Filgas, R.; Hartmann, D. H.; Yoldaş, A.; Nardini, M.; E., Felipe Olivares; Rau, A.; Rossi, A.; Schady, P.; Updike, A. C.

doi:10.1051/0004-6361/201015458

Cited by 229 publications

(388 citation statements)

References 66 publications

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“…In the late afterglow, ν i < ν c (the slow cooling regime) and the optical wavelength range is located either above or below ν c , which is fully supported by current observations (e.g. Galama & Wijers 2001;Stratta et al 2004;Nardini et al 2006;Schady et al 2007;Greiner et al 2011). Two prominent signatures, the Ly-α and Lyman-limit break at 121.5 × (1 + z) nm and 91.2 × (1 + z) nm respectively, and their characteristic redshift-dependent prominence, allow for a robust and precise redshift determination.…”

Section: Introductionsupporting

confidence: 84%

Photometric redshifts for gamma-ray burst afterglows from GROND andSwift/UVOT

Krühler

Schady

Greiner

et al. 2011

A&A

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Aims. We present a framework to obtain photometric redshifts (photo-zs) for gamma-ray burst afterglows. Using multi-band photometry from GROND and Swift/UVOT, photo-zs are derived for five GRBs for which spectroscopic redshifts are not available. Methods. We use UV/optical/NIR data and synthetic photometry based on afterglow observations and theory to derive the photometric redshifts of GRBs and their accuracy. Taking into account the afterglow synchrotron emission properties, we investigate the application of photometry to derive redshifts in a theoretical range between z ∼ 1 to z ∼ 12.Results. The measurement of photo-zs for GRB afterglows provides a quick, robust and reliable determination of the distance scale to the burst, particularly in those cases where spectroscopic observations in the optical/NIR range cannot be obtained. Given a sufficiently bright and mildly reddened afterglow, the relative photo-z accuracy η = Δz/(1 + z) is better than 10% between z = 1.5 and z ∼ 7 and better than 5% between z = 2 and z = 6. We detail the approach on 5 sources without spectroscopic redshifts observed with UVOT on-board Swift and/or GROND. The distance scale to those same afterglows is measured to be z = 4.31 +0.14 −0.15 for GRB 080825B, z = 2.13 +0.14 −0.20 for GRB 080906, z = 3.44 +0.15 −0.32 for GRB 081228, z = 2.03 +0.16 −0.14 for GRB 081230 and z = 1.28 +0.16 −0.15 for GRB 090530. Conclusions. Due to the exceptional luminosity and simple continuum spectrum of GRB afterglows, photometric redshifts can be obtained to an accuracy as good as η ∼ 0.03 over a large redshift range including robust (η ∼ 0.1) measurements in the ultra-high redshift regime (z 7). Combining the response from UVOT with ground-based observatories and in particular GROND operating in the optical/NIR wavelength regime, reliable photo-zs can be obtained from z ∼ 1.0 out to z ∼ 10, and possibly even at higher redshifts in some favorable cases, provided that these GRBs exist, are localized quickly, have sufficiently bright afterglows and are not heavily obscured.

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Section: Introductionsupporting

confidence: 84%

Photometric redshifts for gamma-ray burst afterglows from GROND andSwift/UVOT

Krühler

Schady

Greiner

et al. 2011

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“…For this event, Greiner et al (2011) found that different pairs of (z, A V ) solutions can explain the non-detection of the optical/NIR afterglow by GROND. For example, for a redshift of 3.5 a host extinction of A host V = 1.5 mag is required.…”

Section: Host Galaxy Candidates Of Truly Dark Burstsmentioning

confidence: 88%

“…In addition, it is found that while extinction by dust in GRBHs along the lines of sight is usually rather small, a long tail of A&A 545, A77 (2012) possible extinction values is apparent in the data (cf. Kann et al 2010;Greiner et al 2011;Krühler et al 2011), implying that at least some optical afterglows are extinguished by dust in their host galaxies.…”

Section: Optical Afterglowsmentioning

confidence: 99%

“…This conclusion then naturally leads to the question of whether extinction by cosmic dust can explain the entire ensemble of optically dark bursts or whether their high redshifts (seen as Lyman dropouts) is also an important factor. This question was finally answered when Greiner et al (2011), based on a homogeneous data set of multi-color follow-up observations of bursts, were able to show that extinction by dust in the GRBHs is the main reason for the optical dimness of most dark events. This was later confirmed by Melandri et al (2012) in an independent analysis of a complete sample of bright Swift bursts.…”

Section: Bursts With Optically Undetected Afterglowsmentioning

confidence: 99%

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A deep search for the host galaxies of gamma-ray bursts with no detected optical afterglow

Rossi

Klose

Ferrero

et al. 2012

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Context. Gamma-ray bursts (GRBs) can provide information about star formation at high redshifts. Even in the absence of a bright optical/nearinfrared/radio afterglow, the high detection rate of X-ray afterglows by Swift/XRT and its localization precision of 2-3 arcsec facilitates the identification and the study of GRB host galaxies. Aims. We focus on the search for the host galaxies of 17 bursts with arcsec-sized XRT error circles but no detected long-wavelength afterglow, in spite of their deep and rapid follow-up observations. Three of these events can also be classified as truly dark bursts, i.e., the observed upper limit on the optical flux of the afterglow was less than expected based on the measured X-ray flux. Our goals are to identify the GRB host galaxy candidates and characterize their phenomenological parameters. Methods. Our study is based on deep R C and K s -band observations performed with FORS1, FORS2, VIMOS, ISAAC, and HAWK-I at the ESO/VLT, partly supported by observations with the seven-channel imager GROND at the 2.2-m telescope on La Silla, and supplemented by observations with NEWFIRM at the 4-m telescope on Kitt Peak. To be conservative, we searched for host galaxy candidates within an area of twice the radius of each associated 90% c.l. Swift/XRT error circle. Results. For 15 of the 17 bursts, we find at least one galaxy within the searching area, and in the remaining two cases only a deep upper limit to R C and K s can be provided. In seven cases, we discover extremely red objects in the error circles, at least four of which might be dust-enshrouded galaxies. The most remarkable case is the host of GRB 080207, which has a color of (R C − K s ) AB ∼ 4.7 mag, and is one of the reddest galaxies ever associated with a GRB. As a by-product of our study we identify the optical afterglow of GRB 070517. Conclusions. Only a minority of optically dim afterglows are due to Lyman dropout ( 1/3). Extinction by dust in the host galaxies might explain all other events. Thereby, a seemingly non-negligible fraction of these hosts are globally dust-enshrouded, extremely red galaxies. This suggests that at least a fraction of GRB afterglows trace a subpopulation of massive starburst galaxies, which are markedly different from the main body of the GRB host galaxy population, namely the blue, subluminous, compact galaxies.

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“…Hence, the effect that causes the unusual spectral shape in the afterglow of GRB 140506A may be important for the understanding of the dark burst phenomenon Jakobsson et al 2004a;Greiner et al 2011;Krühler et al 2011;Rossi et al 2012;Perley et al 2013). …”

Section: Implications For Dark Grbsmentioning

confidence: 99%

The mysterious optical afterglow spectrum of GRB 140506A atz= 0.889

Fynbo

Krühler

Leighly

et al. 2014

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Context. Gamma-ray burst (GRB) afterglows probe sightlines to star-forming regions in distant star-forming galaxies. Here we present a study of the peculiar afterglow spectrum of the z = 0.889 Swift GRB 140506A. Aims. Our aim is to understand the origin of the very unusual properties of the absorption along the line of sight. Methods. We analyse spectroscopic observations obtained with the X-shooter spectrograph mounted on the ESO/VLT at two epochs 8.8 h and 33 h after the burst, and with imaging from the GROND instrument. We also present imaging and spectroscopy of the host galaxy obtained with the Magellan telescope. Results. The underlying afterglow appears to be a typical afterglow of a long-duration GRB. However, the material along the line of sight has imprinted very unusual features on the spectrum. First, there is a very broad and strong flux drop below 8000 Å (∼4000 Å in the rest frame), which seems to be variable between the two spectroscopic epochs. We can reproduce the flux-drops both as a giant 2175 Å extinction bump and as an effect of multiple scattering on dust grains in a dense environment. Second, we detect absorption lines from excited H i and He i. We also detect molecular absorption from CH + . Conclusions. We interpret the unusual properties of these spectra as reflecting the presence of three distinct regions along the line of sight: the excited He i absorption originates from an H ii-region, whereas the Balmer absorption must originate from an associated photodissociation region.The strong metal line and molecular absorption and the dust extinction must originate from a third, cooler region along the line of sight. The presence of at least three separate regions is reflected in the fact that the different absorption components have different velocities relative to the systemic redshift of the host galaxy.

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The nature of “dark” gamma-ray bursts

Cited by 229 publications

References 66 publications

Photometric redshifts for gamma-ray burst afterglows from GROND andSwift/UVOT

Photometric redshifts for gamma-ray burst afterglows from GROND andSwift/UVOT

A deep search for the host galaxies of gamma-ray bursts with no detected optical afterglow

The mysterious optical afterglow spectrum of GRB 140506A atz= 0.889

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